1. Field of the Invention
The present invention relates to a fuel supply control apparatus for an engine that is capable of using any one of alcohol, gasoline, and alcohol-gasoline mixture as fuel.
2. Description of Related Art
A conventional fuel supply control apparatus for an engine that is capable of using any one of alcohol, gasoline, and mixture of alcohol and gasoline is shown in JP-A-S62-178735, for example. The apparatus in JP-A-S62-178735 detects an alcohol concentration in blended fuel by using a capacitance sensor. As the alcohol concentration in blended fuel becomes higher, or as the coolant temperature of the engine becomes lower, an injection duration of a fuel injection valve is made longer such that an amount of fuel supplied to the engine is increased. As a result, when starting the engine at a low-temperature state, the starting of the engine is reliably executed.
When water is mixed with blended fuel, a capacitance of blended fuel is increased, and thereby the alcohol concentration detected by the capacitance sensor may have an erroneous detection value. Specifically, the alcohol concentration detected by the sensor may become higher than an actual alcohol concentration. As a result, specially when the engine is started during the low temperature state (when the engine is cold-started), fuel may be excessively supplied to the engine. As a result, the fuel consumption is disadvantageously increased, and at the same time, drivability may deteriorate disadvantageously.
It should be noted that a detected alcohol concentration detected by a capacitance sensor is higher than an actual alcohol concentration when water is mixed with blended fuel disadvantageously. Also, for example, a detected alcohol concentration detected by a known optical type sensor is higher than the actual alcohol concentration when water is mixed with blended fuel disadvantageously.